Trajectories in the first quadrant of a heated Yukawa cluster during . Each one arbitrary particle is highlighted in the central, middle, and outer region. The gray pattern around the origin indicates the array scanned by the laser spots. Parameters: particle number N = 200, screening parameter , equilibrium Coulomb coupling parameter , friction parameter , and heating power .
Time evolution of the local temperature in the simulation for different radii. The lasers were “turned on” at t = 0. While the temperature at the inside (top curve) saturates on a time scale , the relaxation is slower for the outer particles with . The temperatures were averaged over 40 independent simulations. Parameters: N = 200, . Prior to heating the cluster is in the crystal state.
Velocity distribution of particles within concentric rings (N = 200, moderate heating power , equilibrium coupling strength ). The data points are well fit by Gaussians (filled curves) with decreasing width . The velocity distribution in y-direction coincides with and is not shown. The heated area is indicated by the gray pattern.
The simulation data (symbols in upper plot, N = 200, ) are fit by both a logarithmic temperature profile and by modified Bessel functions, Eq. (8) . The latter fits the data well while the former solution does not. The central region was excluded from the fits since the power input by the lasers takes place in this region. The spatial density (lower plot) is almost constant in the central region where most of the heat loss to the neutral gas takes place.
Simulation data (symbols) and fits by modified Bessel functions (lines) for different equilibrium temperatures and constant heating power . The central region was always excluded. On the right axis, the temperature is translated into a local coupling parameter (averaging over the shells 20 ).
Simulation data (points) and fits by modified Bessel functions (lines) for different heating powers. The central region was always excluded. The equilibrium temperatures corresponds to in all cases.
Values of the parameter b for different equilibrium temperatures . Each symbol represents a single simulation. The error bars show the variance of the single estimates of b. Parameters: N = 200, .
Values of the parameter b for different equilibrium temperatures of the Langevin thermostat (left) and for different heating powers (right). Each symbol represents the average from 20 independent simulations with the variance of this average as error bar. The horizontal dashed lines indicate the mean value of for and for in dimensionless units. The power dependence is well reproduced by a linear fit, , with and . Simulation parameters: N = 200, .
(a) Dependence of the fitted decay parameter b (growing curves) and the corresponding decay length L (decreasing curves) on the friction coefficient γ. (b) The heat conduction k appears constant a high γ while it increases when γ is being reduced, for . (c) The mobility of the dust grains is characterized by the MSD, see text, at a time difference in units of .
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